Field of the Invention
The present invention relates to a light source apparatus, an image display apparatus and a control method for a light source apparatus.
Description of the Related Art
There are color image display apparatuses including a color liquid-crystal panel having a color filter and a light source apparatus (backlight apparatus) which irradiates white light onto the rear surface of the color liquid-crystal panel. Conventionally, a fluorescent lamp, such as a cold-cathode fluorescent lamp (CCFL), or the like, is mainly used as a light source for a light source apparatus. However, in recent years, light-emitting diodes (LED), which are excellent in terms of power consumption, lifespan, color reproduction and environmental burden, have come to be used as a light source for light source apparatuses.
A light source apparatus which uses an LED as a light source (LED backlight apparatus) generally has a plurality of LEDs. Japanese Patent Application Publication No. 2001-142409 discloses an LED backlight apparatus having a plurality of light-emitting blocks. The light-emitting blocks each have one or more LED. Furthermore, Japanese Patent Application Publication No. 2001-142409 indicates that the light emission brightness of each of the plurality of light-emitting blocks is controlled individually.
By reducing the light emission brightness of light-emitting blocks which irradiate light onto a low-brightness display region of the screen of the color image display apparatus, it is possible to reduce the power consumption and to improve the contrast of the display image (the image displayed on the screen). A low-brightness display region is a region where a dark image is displayed. Furthermore, by increasing the light emission brightness of the light-emitting blocks which irradiate light onto a high-brightness display region of the screen, it is possible to improve the contrast of the display image, and it becomes possible to portray glare and sparkle that could not be portrayed conventionally. A high-brightness display region is a region where a bright image is displayed. By reducing the light emission brightness of the light-emitting blocks which irradiate light onto the low-brightness display region and raising the light emission brightness of the light-emitting blocks which irradiate light onto the high-brightness display region, it is possible to further improve the contrast of the display image. The light emission control of the respective light-emitting blocks corresponding to the characteristics of the image is called “local dimming control”. Furthermore, local dimming control which raises the light emission brightness of the light-emitting blocks that irradiates light onto the high-brightness display region is called “high dynamic range (HDR) control”.
In general, it is desirable for the power consumption of the apparatus to be small. As described above, there is local dimming control which is capable of reducing the power consumption. However, light source apparatuses are not necessarily capable of carrying out local dimming control of this kind. Furthermore, the user may not necessarily want local dimming control. Therefore, a new method is required which is capable of reducing the power consumption even when local dimming control is not carried out.